Most yo-yos are in the form of two disk-shaped side portions that are rigidly connected to each other by some form of axle structure. The side portions are usually of unitary construction and are made out of plastic, metal or wood. The axle structure is secured to the center of both side portions and may be an assembly of multiple parts, or merely be in the form of a dowel or a riveted pin. In many modern yo-yos, the axle structure includes a center-located bearing or other member that is secured to, and rotatable on, an elongated axle pin.
The axle structure also forms an anchor for one end of a string-type tether. An end-located loop portion of the tether is positioned so that it encircles a center portion of the axle structure. The free end of the tether is usually tied to create a second loop portion that can be placed about one of a user's fingers to thereby secure the yo-yo to the user's hand.
When the tether is wound about the axle structure and the yo-yo is released, or thrown, from the user's hand, the yo-yo will begin to rapidly spin as it moves away from the user's hand and the tether unwinds from the axle structure. Once the tether is fully unwound, the yo-yo may “sleep” at the end of the tether, whereby the yo-yo's side portions continue to spin without the tether rewinding on the axle structure. Once the yo-yo is sleeping, there are a number of tricks, such as “walk the dog,” that a person can perform with the spinning yo-yo. A sleeping yo-yo is also often used to perform tricks that involve temporarily placing the spinning yo-yo onto a portion of the tether intermediate of the tether's two ends.
At the completion of most yo-yo tricks, the user will make a quick tug/jerk on the tether. This will result in a brief tightening of the tether, which is then automatically followed by a temporary slackening of the tether. Once the tether goes slack, the tether's twist will cause one or more portions of the tether located proximate the axle structure to move, and thereby contact, a spinning portion of the yo-yo. Once contact has occurred, the tether portion can become locked to a spinning portion of the yo-yo in a manner whereby rotation of the spinning portion of the yo-yo causes the tether to wind about the axle structure. Winding of the tether on the axle structure makes the yo-yo return to the user's hand.
Every yo-yo has three crucial performance characteristics that determine the yo-yo's ability to perform tricks. They are the yo-yo's potential sleep time, its ability to return on command, and whether the yo-yo is smooth on the tether.
Concerning a yo-yo's sleep time, the longer the yo-yo can be made to sleep, the more time the user will have to complete any particular yo-yo trick. It is well known that by minimizing friction in the yo-yo's components, one can maximize the yo-yo's sleep time. Furthermore, it is known that whenever the tether even slightly rubs against a spinning portion of the yo-yo, the created friction will reduce the yo-yo's sleep time.
For a yo-yo to return on command, the structure and design of the yo-yo must be such that when the user causes the tether to briefly go slack, a portion of the tether can become locked to a spinning portion of the yo-yo in a manner whereby the yo-yo is caused to return to the user's hand. In most prior art yo-yos, the ability for the tether to become locked to a spinning portion of the yo-yo is usually enhanced through the use of engagement adaptations, such as raised ribs, located on an inner portion of the tether-facing surface of both of the yo-yo's side portions. The tether-facing surface of a side portion is herein defined as the surface of the side portion that faces a portion of the yo-yo's tether when said tether extends straight out from the yo-yo's string gap area. A yo-yo's string gap area is herein defined as the area located between the yo-yo's side portions. The ability of a yo-yo to return on command is also the common measure of a yo-yo's responsiveness.
Concerning a yo-yo's ability to be smooth on the tether, this refers to a yo-yo's ability, when it is sleeping at the end of the tether, to be temporarily placed on a medial portion of the tether without the tether becoming locked to a spinning portion of the yo-yo. An example of a trick that requires a yo-yo to be smooth on the tether is “man on the trapeze.” If, during such a trick, the yo-yo can slide on the tether, the yo-yo is said to be very smooth on the tether/string. The ability of a yo-yo to be smooth on the tether is favored when the yo-yo's responsiveness is low. A yo-yo with an overly high responsiveness will transform even the slightest contact between the tether and a spinning portion of the yo-yo into an inadvertent rapid return of the yo-yo to the user's hand. When such an inadvertent return happens, the performance of a yo-yo trick will usually be cut short and thereby ruined.
Over the years, many different shapes have been employed for the yo-yo's side portions. Traditional yo-yos will usually feature substantially planar side portions that have a bulge in the area of the rim to provide an improved weight distribution that increases spin time and stability. Butterfly yo-yos feature side portions that are stretched outwardly, away from the center of the yo-yo, thereby increasing the width of the yo-yo and giving the yo-yo a butterfly shape when viewed in cross-section.
It is also known to use different materials for, or on, the rim portion of each of a yo-yo's side portions. For example, while most yo-yos have rim portions made of a hard plastic material, it is known to employ rubber either as the rim material, or in the form of an o-ring that is placed on the periphery of each of a yo-yo's side portions.
The different shapes and materials employed in a yo-yo's side portions not only make the yo-yo distinctive, they also affect the yo-yo's performance. For example, a user performing looping tricks with a yo-yo will usually prefer a traditionally shaped yo-yo that has substantially planar side portions. Such a shape is best at looping since the weight distribution is close to the tether's attachment point on the yo-yo, thereby enabling the yo-yo to flip over relatively easily during each loop. For yo-yo tricks in which the user attempts to catch the spinning yo-yo on a medial portion of the tether, a butterfly shaped yo-yo is preferred. The more widely spaced-apart side portions improve the yo-yo's stability whereby the yo-yo is less prone to tilt off the tether. Furthermore, the wider stance of a butterfly-shaped yo-yo facilitates a user being able to land the yo-yo on a medial portion of the tether.
To take advantage of the different yo-yo performance characteristics provided through the use of side portions of different shapes and/or materials and/or that have different tether engagement adaptations, many experienced yo-yo players will own a large variety of different yo-yos. This enables the player to pick a yo-yo from his or her collection that will work best for the particular trick(s) that the player wishes to perform. However, the costs involved in buying and maintaining a large number of yo-yos can be considerable. In addition, transporting a large number of yo-yos can be bothersome and is usually accomplished using a bulky and expensive transport case specially adapted for carrying yo-yos.